Process for the chlorination of aminoanthraquinone compounds



Patented Aug. 23, 1938 PATENT OFFICE.

PROCESS FOR THE CHLORINATION OF AMINOANTHRAQUINONE COMPOUNDS William Dettwyler, Milwaukee, Wis., assignor to E. I. du Pont de Nemours &' Company, Wilmington, Del., a corporation of Delaware No Drawing.

Application November 23, 1936,

Serial N 0. 112,353

3 Claims.

This invention relates to a new and improved process for the preparation of chlorinated aminoanthraquinones.

While it is known that both alphaand betaaminoanthraquinones can be halogenated to give, in the first case, 1-amino-2,4-dihalogenoan thraquinone and, in the second case, 1,3-dihalogeno-2-aminoanthraquinone, it has been recog nized that the chlorination of these aminoanthraquinones does not take place with the same ease as the bromination, and that the yields and purity of the chloro-compounds do not compare with those obtained by bromination. For this reason, the dibromoaminoanthraquinones have been employed wherever it was possible.

Chlorination of aminoanthraquinones in organic solvents according to known methods gives poor yields of a product of low purity. More recent use of hydrochloric acid or acetic acid, or mixtures of the two, has given improved yields and a relatively pure product. both of these acids are volatile'acids and quite corrosive, they offer mechanical difficulties which together with their cost make their use undesirable if it can be avoided.

It is therefore an object of this invention to provide a new and improved method for chlorinating aminoanthraquinones which is inexpensive to operate and which will give high yields of a relatively pure product.

It is a further object to provide a method for chlorinating aminoanthraquinones in sulfuric acid of from 45 to 55% concentration, whereby complete chlorination takes place with a minimum formation of undesired products, and by the use of which the cost of preparing these products is substantially decreased.

I have found that high yields of relatively pure chlorinated aminoanthraquinones can be obtained by carrying out the chlorination of the aminoanthraquinone in sulfuric acid of from 45 to 55% and at room temperature, under which conditions both the 2-4 positions of the alphaaminoanthraquinone and the 1-3 positions of the beta-aminoanthraquinone are completely chlorinated with substantially no formation of side reaction products. Using higher concentrations of sulfuric acid, oxidation of the aminoanthraquinone takes place together with a loss of material quantities of chlorine. Where acid of less than 45% is used, complete chlorination does not take place and some oxidation products are produced resulting in poor yields of a very impure final product.

According to the present invention the amino- However, since anthraquinone is added to the sulfuric acid of from 45 to 55% concentration in which it is converted to the sulfate of the amine which, not being soluble in the dilute acid; remains suspended therein under agitation. The amount of acid used may be varied within wide limits, although it is desirable to use suflicient acid to give a readily stirrable mass. Ten to fifteen parts of acid to each part of aminoanthraquinone are sufiicient. The chlorination is then effected by the usualand known methods, such as bythe addition of sodium chloride and sodium chlorate or other oxi dizing agents. Addition of the oxidizing agent. should be governed by the rate at which the chlorine is used up. The temperature is" preferably kept between 20 and 30 C., although somewhat higher or lower temperatures are op erable. Too high a temperature results in loss of chlorine and increases the tendency to produce undesirable oxidation products. Attoo low a temperature the chlorination is retarded. As the aminoanthraquinone is chlorinated it is also hydrolyzed to the free base in which form it. is also insoluble in the dilute acid and is readily. filtered off and washed acid free. 1.

As illustrated in the following examples, the process is applicable to chlorination of the heteronuclear diaminoanthraquinones as well as to the mono-amines, and also to the alphaor beta-aminoanthraquinones which may contain chlorine in the 5, 6, '7 or 8 position.

The following examples are given to more fully illustrate the invention, it being understood that these are given by way of illustration and not with any intention of limiting the invention thereto. The parts used are by weight.

Example 1 100 parts finely ground 2-aminoanthraquinone are added under good agitation to 1200 parts 50% sulfuric acid, the temperature is permitted to rise to 4050 C., 200 parts common salt are then added and the mass is cooled to 30 C. The flask is closed in such a manner that no inside pressure can be built up, and over a period of 5 to 8 hours 40 parts sodium chlorate are added in small portions while the temperature is held at from 25 to 30 C. The additions are timed so that all chlorine is used up before more chlorate is added. When all the chlorate is charged, the mass is stirred at room temperature for 10 hours and diluted in 5000 parts of hot water, filtered, and washed acid-free. The cake is suspended in 3000 parts of hot water and 30 parts of soda ash are added. It is then stirred at 60 to 70 C. for

one hour, filtered and washed until the filtrate runs water-clear.

1,3dichloro-2-aminoanthraquinone is obtained in substantially pure form in a yield of over 85% of theory.

Example 2 V 100 parts l-aminoanthraquinone are suspended in 1200 parts 50% sulfuric acid and stirred until the formation of the sulfate is complete.

200 parts sodium chloride are then added and the 7 Example 3 To a'suspension of 1200*parts 50% sulfuric acid and '50 parts I-amino-8-chloroanthraquinone, 100 parts sodium chloride are added. The temperature is then adjustedto 25 C. and there are added in small portions over a period of 3 to 4 hours, at 25 to 30 CL, 20 parts sodium chlorate.

The first red colored suspension changes gradually to an orange-red as the chlorination proceeds; When all the chlorate is charged, the

. mass is stirred foran additional 10 to 12 hours.

It is then'diluted, filtered and washed acid-free. The cake is extracted with a' /2% soda ash solution, filtered and washed dry. The so obtained product is a Famine-2,4,8-trich1oroanthraquinone and contains 32.4% chlorine.

Example 4 By using the 1-amino-5-chloroanthraquinone,

the isomeric 1-amino-2,4,5-trichloroanthraquinone may be obtained.

The Cake '15 excomes gradually orange.

Example 5 cellent yields.

Example 6 50 parts 2,6-diaminoanthraquinone are suspended ln 1200 parts of 50% sulfuric acid and 125 parts-salt are added. 40 parts of sodium chlorate are then added at 25 to 30 C. over a period of 4. to 5 hours. The first gray-brown mass be- After stirring more hours, the mass is diluted to about 10% sulfuric acid, filtered and washed acid-free. The cake is extracted with dilute soda ash solution, filtered and washed dry. The 2,6-diamino-1,3,5,7-tetrachloroanthraquinone containing 36.5% chlorine is obtained in highyields. 7

I claim:

l.- In the process for preparing chlorinated primary aminoanthraquinone compounds, the step which comprises carrying out the chlorination' in sulfuric 'acid of a concentration of from 45' to 55%.

2. In the process for chlorinating primary aminoanthraquinones, the steps which comprise suspending the aminoanthraquinone in sulfuric acid of from 45 to 55%, whereby-the amine sulfate is formed, and slowly chlorinating the mass to produce the aminochloroanthraquinone.

3. The process for preparing 1,3-dichloro-2- aminoanthraquinone which comprises suspending beta-aminoanthraquinone in an aqueous solution of sulfuric acid of from 45 to 55% concentration, and chlorinating the mass until dichlorination of the'beta-aminoanthraquinone has been completed.

WILLIAM DET'I'WYLER. 

